1. Field of the Invention
This invention in general relates to the testing of transducers, and more particularly is directed to a novel transducer structure to permit simplified testing and calibration.
2. Description of the Prior Art
Various methods exist for the testing of transducer arrays which for example may be found in homing torpedos. The array and its associated signal processing electronics must be tested to see that each individual transducer is operating properly within prescribed limits. Further, it is often desired to test the beam steering operation of the entire array of transducers.
Proper operation may be determined at the point of manufacture or at a large test facility by placing at least the transducer array portion of the torpedo into a large test tank and applying preprogrammed signals to the transducer array for testing in the transmit mode of operation. The receive mode of operation may be tested by placing acoustic sources in the tank and projecting acoustic energy to the array to simulate a target.
Another testing device involves the use of what is called an "inverse transducer" which is a transducer system that creates an equivalent acoustic plane wave front that is steerable. The inverse transducer is placed against the torpedo array face and then forced into intimate contact by the application of tons of force.
Both of the above test methods are adequate for initial testing at large facilities however it is also desired to check out the torpedo before launch, a process which includes the testing of the transducer array. Under such circumstances, and particularly where the torpedo is air-launched, space and weight may be at a premium and such testing methods are not possible or practical.
In an effort to save the weight of heavy testing equipment and with a view toward portability, a method has been proposed for testing the array wherein a special electrode is placed on the transducer active element to couple in preprogrammed test signals. A problem arises however in that the active element is supplied with signals at a relatively high voltage level which can cause arcing over to the leads going to the calibrating and testing circuitry. Further, in addition to the arc over problem, the special electrode picks off a portion of the applied signal and unless auxiliary protection circuitry is provided, the relatively high voltage picked off by the special electrode can completely burn out the calibration and test circuitry.